Have they been around for long, and you know of any external public audit that has been done on them?
They are DIN ISO/IEC 27001 certified: https://www.hetzner.com/unternehmen/zertifizierung. Of course if you only store encrypted data you don't really need this auditing.
[1] https://www.hetzner.com/dedicated-rootserver
Have they been around for long, and you know of any external public audit that has been done on them?